1. Field of the Invention
The invention relates to a multilayer web plate comprised of plastic material. The web plate comprises two generally planar outer walls, and further comprises structural webs joining the walls to form a unit construction. The outer walls are each comprised of a plurality of adhesively joined layers comprised of different plastic materials. Web plates of this type can be fabricated by extrusion, and as a rule have the same profile over their entire length in the extrusion direction.
2. Discussion of the Background
A multilayer web plate is known from Eur. OS A No. 110,221. The outer walls of the web plate are comprised of a supporting layer of polycarbonate plastic, an intermediate layer of modified polycarbonate plastic, and a surface layer of polymethyl methacrylate. The layered structure serves to improve resistance to ultraviolet light and to improve manufacturing qualities.
Another multilayer web plate is disclosed in Eur. OS A No. 118,683. The outer walls are comprised of a supporting outer layer of an acrylic glass substitute and a thinner inner layer of a high impact plastic, e.g., polycarbonate, whereby overall high impact resistance is attained.
According to Ger. AS No. 16 94 273, a pane comprised of polycarbonate plastic is coated with a polymethyl methacrylate varnish, whereby the light-permeability of the pane is slightly improved.
A disadvantage of known two-wall web plates having outer walls with a single-layer or multilayer structure is that they have low light-permeability. Even if they are manufactured from maximally clear polycarbonate plastic, with the webs disposed perpendicularly to the outer walls, the light-permeability is only about 78%. If the outer walls are coated with a polymethyl methacrylate varnish according to the teaching of Ger. AS No. 16 94 273, the light-permeability is increased only slightly, to 80%.
Accordingly, the underlying problem to be solved by the invention is to substantially increase the light-permeability of plastic web plates without altering their spatial dimensions (e.g., the disposition and number of webs).